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AGL's Liddell plant heading to oblivion

The woman in charge of keeping Liddell power station running on a daily basis has warned it's on "a sliding scale to oblivion".

Energy giant AGL is under pressure from the Turnbull government to keep the geriatric coal-fired generator in the NSW Hunter Valley open beyond its planned 2022 closure.

But the company expects it will cost $150 million just to keep the station running for the five years until then.

That comes on top of almost $138 million it's spent in the three years since it bought Liddell, and the newer and neighbouring Bayswater generator from the NSW government.

AGL Macquarie general manager Kate Coates doesn't think it's worth keeping the plant open past 2022, when it will be 50 years old.

"I think we can spend our resources and spend our people's time elsewhere," she told reporters at the power station on Tuesday

Problems with the plant include water leaking into electrical systems, a rusty and rickety coal conveyor system, an ash disposal dam that will be full in 2022, and hundreds of kilometres of eroding pipes.

But the biggest problem is leaks in the boiler tubes, caused by a range of issues, largely related to the age of the generator and repeated stresses on the metal during the normal course of operations.

One of the four boilers was out of action during the February heatwave when an aluminium smelter had to close down or risk wider blackouts in NSW.

"(The station) is on a sliding scale to oblivion, frankly," Ms Coates said.

"The failures become more regular, the weak points larger and more numerous. We are fighting a losing battle."

An independent report prepared for the NSW government in 2013 - before it sold the power station - estimated that to keep Liddell running from 2022 to 2032 would cost $900 million.

AGL hasn't yet done its own updated, detailed assessment of whether that figure still holds.

Ms Coates says recent scrutiny of the power station's future had taken a toll on workers.

"One of the advantages we have with the seven years' notice (AGL chief executive) Andy Vesey gave us ... and the consistency he's given us is that we can start planning for what our staff will be doing," she said.

"We had a clear view, a clear direction. We haven't changed our direction but our people now are very confused, they're very stressed and I think this uncertainty has really caused a great deal of anxiety in the workforce."